Lithographic technology using extreme ultraviolet (EUV) light as exposure light to implement miniaturization of a semiconductor device, has been proposed.
In EUV lithography, increase in sensitivity of a resist film becomes important since an output of an EUV light source can hardly be increased. For this reason, containing a substance which increases absorption of the exposure light in the resist film has been proposed. However, if a light absorption coefficient is constant in a thickness direction of the resist film, an amount of absorbed light is decreased from a top surface toward a bottom surface of the resist film. Thus, a sufficient exposure amount can hardly be secured along the thickness direction of the resist film.
A method of disposing a lower layer film containing a sensitizer which increases the sensitivity to the exposure light under the resist film and diffusing the sensitizer from the lower layer film into the resist film has been proposed as a solution to such a problem. To prevent mixing of the lower layer film and the resist film, however, the lower layer film needs to be sufficiently cured at a high temperature prior to formation of the resist film. In other words, the lower layer film needs to be cured at a temperature higher than a temperature at which the sensitizer is diffused from the lower layer film into the resist film. Thus, a problem arises that the sensitizer can hardly be diffused from the lower layer film into the resist film.
A method of urging the sensitizer to be sufficiently contained into the resist film is therefore desired.